Due to a trend of miniaturization of current mobile broadband products and an increasingly complicated electromagnetic environment around an antenna, an antenna signal is generally subject to interference from a second harmonic. For that reason, signal interference caused by the second harmonic may be generally suppressed by setting an LC (inductor-capacitor) trap network. FIG. 1 is a schematic structural diagram of an existing harmonic suppression system. As shown in FIG. 1, the system includes an interface connector 11, an LC trap network 12, a baseband chip 13, an antenna switch 14, and an antenna 15, where the LC trap network 12 is connected between the interface connector 11 and the baseband chip 13, and configured to suppress a second harmonic that occurs when an operating frequency band of the antenna 15 is a frequency band corresponding to the LC trap network 12; and the antenna switch 14 is connected between the baseband chip 13 and the antenna 15, and configured to enable the baseband chip 13 to control the operating frequency band of the antenna 15 using the antenna switch 14.
As shown in FIG. 1, suppression of a second harmonic in a case of this frequency band can be implemented using this solution only when the operating frequency band of the antenna 15 is the frequency band corresponding to the LC trap network 12. However, the operating frequency band of the antenna 15 may generally cover multiple frequency bands; therefore, based on the foregoing existing solution, when the operating frequency band of the antenna 15 is another frequency band, suppression of a second harmonic in a case of the another frequency band cannot be implemented using the LC trap network 12.